The determination of total oxygen demand of combustible materials in aqueous dispersion is usefully adopted in the field of pollution control. Water pollution control is a long standing problem and ever increasing in importance as population and various industries continue to grow in relation to water resources.
As a hitherto known method for determining the total oxygen demand of combustible materials in aqueous dispersion, there is, for example, a method described in the specifications of U.S. Pat. No. 3,560,156.
According to this method, the concentration of oxygen in a feed gas stream composed of an inert gas containing oxygen must be maintained within a narrow range from 10 to 10,000 parts per million. This limitation makes it difficult to utilize air, which is inexpensive, and has a relatively stable ratio of components existing throughout the world, as a feed gas stream.
Also, according to this method, two values of electrical output from an oxygen detector, which changes in relation to the total oxygen demand, are necessary. In applying this prior art, the first value is that registered by the oxygen detector when the sample of combustible materials in aqueous dispersion is not supplied to, nor present in, the feed gas stream. The difference between these two values of electrical output must then be determined after the measurement of the values. Such a method, however, is complicated, high in cost and involves considerable difficulty.
An object of the present invention is to provide a method and an apparatus for determining with very high sensitivity and simplicity the total oxygen demand of combustible materials in aqueous dispersion while avoiding the deficiencies of the prior art.